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Coal characteristics that lead to abrasion during grinding
No full textCurrently in South Africa there is no acceptable standard method for testing coals for abrasion.
Abrasion is the tendency of coals to wear away machinery. The technique referred to as YGP
(Yancey, Geer and Price), proposed and accepted in 1951, is most commonly used to test for
abrasion. Over the years there have been some modifications to this method by both mining
houses and coal users (such as Eskom) which have resulted in inconsistent and conflicting
results. To this end, this study serves as part of a larger project that will aim at devising a
standard method acceptable for testing coals for abrasion in South Africa. The underlying
principle behind this research was to determine the main characteristics in South African run of
mine (ROM) coals that may cause abrasion. This research work specifically seeks to: (1)
determine if the Abrasion Index (AI) and Hardgrove Grindability Index (HGI), empirical
correlations, developed by Scieszka (1985), can be verified using experimental results; (2)
determine if excluded minerals and included minerals are equally abrasive; (3) establish the type
of abrasive wear that occurred during coal grinding. Five ROM coals from the Witbank Coalfields were analysed. An abrasion index tester pot and
Hardgrove machine were used to determine the grinding properties of the coal samples. XRD
(Rietveld method), XRF, Petrography and SEM-EDS were used to characterise the coals samples
in terms of their inorganic and organic components. SEM-EDS was also used for the particle
morphology analysis, and blade surface topography analysis. TGA, moisture oven and sieve
method were used for proximate analysis, moisture analysis, and particle size distribution
analysis respectively.
The results indicated that the key characteristics that influenced the AI of the coal samples were
moisture, vitrinite, and minerals and mineral associations (excluded and included minerals and
carbominerite) and HGI. Results indicated that coal weathering renders coals less abrasive,
compared to unweathered coals. It was concluded that AI and HGI are experimentally
dependent; excluded and included minerals were equally abrasive; and three-body abrasive wear was established to be the main wear during grinding in an abrasion index tester pot
Laser-assisted deposition of titanium and hydroxyapatite biocomposites
Get PDFD.Ing.Biomaterials are required for the tissue engineering applications where they can be used to refunctionalise the broken bones that are unable to heal naturally. Bone healing can be achieved by means of cementless scaffolds made from Ti-6Al-4V alloy. Ti-6Al-4V is biocompatible, because of the apatite layer (TiO2) that readily forms on the surface of the metal; however, this alloy is bio-inert while; bio-integration or chemical bonding is not achieved immediately after implantation. Ti-6Al-4V alloy has low elastic moduli that are closer, but do not match those of the natural bones. Hence, after a while, the implanted scaffold causes wear debris that can lead to inflammatory diseases caused by the leaching of the alloying elements (V ions) into the human body’s fluid system..
Investigation of network microstructure of TiB/Ti6Al4V-ELI composite manufactured with laser metal deposition
Get PDFDATA AVAILABILITY : The dataset generated and analysed during the current
study are available from the corresponding author on reasonable
request.This work presents the microstructural investigation of an in situ synthesized TiB/Ti6Al4V-ELI composite that was manufactured
with additive manufacturing (AM) technique known as laser metal deposition (LMD). A single-track sample was
manufactured by adding TiB2
to Ti6Al4V-ELI at mass deposition volume of 5% and characterized for microstructure and
hardness. It was found that in situ reaction promoted the formation of quasi-continuous network microstructure of TiB whiskers
with a needle-like morphology, in a martensitic α′ matrix. Furthermore, the manufactured TiB/Ti6Al4V-ELI presented
two different grain growth morphologies, with smaller and large TiB network grains observed at the top and bottom of the
sample, respectively, due to heat travelling direction. A high hardness of 513 HV was observed at the top of the sample,
which was reduced to 483 HV at the bottom, promoted by grain growth.The Department of Science and Innovation . Open access funding provided by Council for Scientific and Industrial Research.https://www.springer.com/journal/43580am2024Materials Science and Metallurgical EngineeringSDG-09: Industry, innovation and infrastructur
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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